Intramolecular energy transfer in actinide complexes of 6-methyl-2-(2-pyridyl)-benzimidazole (biz): comparison between Cm3+ and Tb3+ systems

The energy transfer in the Cm3+-biz and Tb3+-biz systems proceeds as depicted in the figure. The curium 6D5/2 and the terbium 5D4 levels serve as the acceptor states for the initial transfers. The curium system displays a highly efficient energy transfer due to the optimal energy difference between the triplet state of the ligand and the accepter level of the metal that minimizes the back transfer processes. In the Tb3+-biz system the donor-acceptor energy gap is only ~600 cm−1. The smaller gap enhances the back transfer rate and the efficiency of the energy transfer is reduced when compared with the curium system.